Compositions comprising a polymer of acrylamide and an amide



United States COMPSSITIGNS CGMPRISLQG A EGLYMER F ACRYLAREBE AND ANAYHDE No Drawing. Application lune 22, 1954, Serial No. 438,606

11 Claims. (Cl. 269-626) This invention relates to new and usefulcompositions of matter and more particularly to compositions comprisingan acrylamide polymerization product and at least one amide selectedfrom the class consisting of urea and formamide.

The compositions of this invention in which urea, more particularlymolten urea, or formamide, or a mixture of urea and formamide in anyproportions, is employed primarily as a solvent or swelling agent forthe acrylamide polymerization product, in which case it constitutes amajor proportion (more than e. g., from to 99% or more, by weight of thecomposition, are particularly useful in the production of shapedarticles therefrom, e. g., filaments, films, threads, rods, tubes andthe like, or as coating, adhesive, laminating, impregnating,paper-treating, tions, etc., or as components of such compositions. Anamide of the kind aforementioned also may be used primarily as aplasticizer for an acrylamide polymerization product, in which case itusually constitutes a minor proportion (less than 50%), e. g., from 0.5to 45%, generally from 1 to 35 or 40%, by weight of the composition. Ifthe product is used or intended for use in an application wherewater-insolubility is important, it can be rendered water-insoluble bysuitable treatment or modification, as by cross-linking with across-linking agent, e. g., methylene-bis-acrylamide, diallyl phthalate,etc.

Polymers and copolymers of acrylamide were known prior to our inventionLikewise it was known that homopolmeric acrylamide and many of thecopolymers of acrylamide are soluble in water. However, to the best ofour knowledge and belief it was not known prior to our invention thatacrylamide polymerization products could be dissolved or swollen incertain organic solvents.

Thus, in a recent article by Shnlz et al., Studies on the radicalpolymerization of acrylamide lMakromol. Chem. 12, 20-34 (1954)], theauthors state: The polyacrylamides prepared by the polymerizationmethods that we have described are soluble in water, but insoluble inordinary solvents such as alcohols, esters, ethers, and hydrocarbons.Among the organic compounds specifically mentioned by the authors asbeing non-solvents for polyacrylamide are tetrahydrofuran,dimethylformamide, nitrobenzene, brornobenzene and tetralin.

The present invention is based on our discovery that polymers andcopolymers of acrylamide, more particularly polymeric (homopolymeric)acrylamide and thermoplastic copolymers of acrylamide, specifically suchcopolymers containing in their molecules an average of at least byweight of combined acrylamide, e. g., copolymers of, by weight, from 75to 99.5% of acryl amide and another monomer such, for instance, as vinylacetate, methyl acrylate, ethyl acrylate, acrylic acid, etc., arecompatible with molten urea, formamide and mixtures of molten urea andformamide, and that such amides are capable of dissolving or swellingthe acryltextile-treating composiatent 6 Ethylene glycol monoethyl iceamide polymerization product to yield solutions or swollen masses whichare suitable for use in a wide variety of industrial applications,examples of which have been given hereinbefore. The invention is basedon out further discovery that the aforementioned amides or mixturesthereof are able efi'ectively to plasticize acrylznnide polymerizationproducts so that the latter more easily can be shaped, as by extrusionor molding, or cast into useful articles of manufacture. The amide employed in practicing our invention may be used either as a temporarymodifier (more particularly, as a temporary plasticizer), that is, amodifier which subsequently is removed from the polymerization product.or as a permanent modifier, specifically plasticizer, which is permittedto remain in the acrylamide homopolymer or copolymer.

The unobvious nature of our invention will be immediately apparent tothose skilled in the art when it is considered that polyacrylamide doesnot dissolve upon being admixed with any of a large number of organiccompounds, even when heated at C. for /2 hour or when heated to boilingand then at boiling for about 10 minutes in the case of those compoundsboiling under 120 C. Thus we have found that finely groundpolyacrylamide does not dissolve, swell, or coalesce, when heated underthe aforementioned conditions, in each of the following compounds:

lsoarnyl alcohol Methacrylic acid Ethylene carbonate Ethylene sulfiteDiallyl carbamate Triallylcyanurate ether Monoethylene glycol monoethylformal Acetic anhydride Maleic anhydride Chloromaleic anhydride Methylethyl ketone Homopolymeric acrylamide and acrylamide copolymers(thermoplastic acrylamide copolymers) containing in the polymermolecules an average of at least 75% by weight of combined acrylamideare employed in carrying the present invention into-effect. Thesepolymers and copolymers are prepared by methods now well known to thoseskilled in the art. in some cases the polymerization rates of theindividual monomers in a polymerizable mixture may be different, withthe result that the proportions of the components in the final copolymerare different from the proportions thereof in the mixture of monomerswhich are polymerized. The proportions of monomers in the polymerizablemixture therefore are preferably adjusted, in practicing the presentinvention, so that y the final copolymer contains in the moleculesthereof an average of at least 75% by weight of combined acrylamide. Theacrylamide polymerization product may be one in which, for example, ahomopolymer of acrylamide has been modified by introducing one or moreother groups into the polymer molecule. For example, the acrylamidepolymerization product may be one in which homopolymeric acrylamide orcertain copolymers of acrylamide have been hydrolyzed under acid oralkaline conditions to introduce carboxylic acid or salt groups into thepolymer molecule or structure, or has been reacted with an aldehyde,specifically formaldehyde, to introduce alkylol, more particularlymethylol, groups into the polymer structure. In such instances, theextent of hydrolysis or alkylolation or other modification is socontrolled that the acrylamide polymerization product still contains atleast 75% by weight of acrylamide units. The expression polymerizationproduct containing in the polymer molecules an average of at least 75%by weight of combined acrylamide, as used herein and in the appendedclaims, means, therefore, a polymerization product (polymer, copolymeror interpolymer, graft polymer, or polymer modified by the introductionof other groups, etc., or mixtures thereof) containing in the moleculesthereof an average of at least 75% by weight of the acrylamide unit,which is considered to be present in the individual polymer molecule asthe group or, otherwise stated, at least 75% by weight of the reactantsubstance converted into and forming or comprising the polymerizationproduct is acrylamide.

Illustrative examples of monomers which may be copolymerized withacrylamide to yield a polymerization product containing in the polymermolecules an average of at least 75% by weight of combined acrylamideare compounds containing a single CHz=C grouping, for instance, thevinyl esters and especially the vinyl esters of saturated aliphaticmonocarboxylic acids, e. g., vinyl acetate, vinyl propionate, vinylbutyrate, etc.; vinyl and vinylidene halides, e. g., the vinyl andvinylidene chlorides, bromides and fluorides; allyl-type alcohols, e.g., allyl alcohol, methallyl alcohol, ethallyl alcohol, etc.; allyl,methallyl and other unsaturated monohydric alcohol esters of monobasicacids, e. g., allyl and methallyl ace-- tates, laurates, cyanides, etc.;acrylic and alkacrylic acids (e. g., methacrylic, ethacrylic, etc.) andesters and amides of such acids other than acrylamide (e. g., methyl,ethyl, propyl, butyl, etc., acrylates and methacrylates, methacrylamide,N-methyl, -ethyl, -propyl, -butyl, etc., acrylamides andmethacrylamides, etc.); methacrylonitrile, ethacrylonitrile and otherhydrocarbon-substituted acrylonitriles; unsaturated aliphatichydrocarbons containing a single CHz=C grouping, e. g., isobutylene,etc.; and numerous other vinyl, acrylic and other compounds containing asingle CH2=C grouping which are copoly merizable with acrylamide toyield thermoplastic copolymers. Alpha,beta-unsaturated polycarboxylicacids and alkyl esters thereof also may be copolymerized with averagemolecular weight) is not less than 10,000 and may be as high as 2million or more. Ordinarily the weight average molecular weight iswithin the range of about 70,000 or 80,000 to 1,600,000-2,000,000. Suchmolecular weights (weight average molecular weights) are determined inthe manner described more fully by P. Flory, Principles of PolymerChemistry, Cornell University Press, 1953, chap. 7, p. 266 et seq.Briefly described the values are ascertained by calculating intrinsicviscosities (limiting viscosity numbers) from measurements of flow timesin an Ostwald viscosimeter at 30.0" C. of any four concentrations of theacrylamide polymerization product below 0.5 g./ 100 ml. in water or 1 Nsodium nitrate solution. The relation between the intrinsic viscosityand the weight average molecular weight is previously established bylight-scattering measurements on a set of eight samples of purepolyacrylamide, in Water, ranging in weight average molecular suchproportions.

4 weight from 78,700 to 1,640,000. The light-scattering measurements areperformed on solutions filtered through ultrafine sintered glass and areinterpreted by standard light-scattering procedures and corrected bydeterminations of dissyrnmetries and depolarization ratios.

The dissolution of the acrylamide polymerization product in, or swellingby, the amide employed in practicing the present invention isaccelerated by using a polymer or copolymer of acrylamide which is in afinely divided state, e. g., one which, if not in a finely divided stateas originally formed, has been ground so that all or substantially allof it will pass through a U. S. Standard Sieve Series No. 50 screen. Italso is usually desirable to agitate the mass, as by mechanicalstirring, While admixing the polymerization product with the solvent. Toavoid or minimize discoloration of the polymeric or copolymericacrylamide, it is generally advantageous to employ the lowest possibletemperature in effecting dissolution, swelling, or plasticization of theacrylamide polymerization product, which temperature is consistent withpractical considerations, e. g., the time required for effectingsolution (or other desired results), etc. With urea alone, the mixturethereof with the polymer of acrylamide should be heated at leastsulficiently high to melt the urea (M. P. of urea, 132.7 C.).

The proportions of the acrylamide polymerization product and amide inthe compositions of our invention may be varied widely, depending mainlyupon the particular use for which the composition is intended. if theamide (urea, formamide or mixture of urea and formamide in anyproportions) is employed primarily as a solvent for the acrylamidehomopolymer or copolymer so as to obtain, for example, a film or othershaped article, or to make a coating, impregnating, laminating,adhesive, textile-treating composition, etc., from which all orsubstantially all of the solvent subsequently is removed, then theacrylamide polymerization product usually constitutes at least 1%, butless than 50%, e. g., from 5% to about or by weight of the composition.Advantageously, in most cases, when the solution is to be used in, forexample, the casting of films, the polymer or coplymer of acrylamideconstiutes at least 5% by weight of the solution.

The formamide solutions of the acrylamide polymerization product areespecially adapted for casting in the form of films. For instance, thehot, liquid composition may be cast upon a revolving drum which ispartly immersed in a coagulating bath of, for example, acetone, methylalcohol, ethyl alcohol, dioxane or dimethyl formamide, and which willserve to deposit the polymerization product as a thin film on the drumas it passes through the bath. Alternatively, formamide solutions of apolymer or copolymer of acrylamide can be cast on a solid surface andthen evaporated in a gaseous atmosphere to form films.

If the amide is to be employed primarily as a plasticizer for theacrylamide polymerization product, then the amide generally constitutesless than 50%, e. g., from 1% to or by weight of the composition (amideplus polymer or copolymer of acrylamide).

The aforementioned ranges of proportions are mentioned as indicative ofproportions that may be employed in forming solutions of, or plasticizedcompositions containing, the acrylamide polymerization product, and ourinvention obviously is not limited to the. use of only portions be suchthat the viscosity or plasticity of the composition at the particularoperating temperature (that is, the temperature at which the compositionis employed) be within a workable range for the particular use to whichthe composition is to be placed.

In order that those skilled in the art may better understand how thepresent invention can be carried into effect, the following examples aregiven'by way of illustration and not by way of limitation. -All partsand percentages are by weight unless otherwise stated.

The important factor is that the pro- Example 1 One (1) part of dryhomopolymeric acrylamide, ground so that substantially all of it passesthrough a U. S. Standard Sieve Series No. 50 screen, is thoroughly mixedwith 99 parts of formamide. (The polyacrylamide employed has a weightaverage molecular weight of about 200,000 as determined by the methodhereinbefore described, that is, by viscometric data related to previouslight-scattering measurements.) The mixture is allowed to stand at roomtemperature (about 30 C.) for 3 days, at the end of which period of timethe polyacrylamide has completely dissolved to form a clear solution.This solution can be cast to yield films as hereinbefore described.Films of plasticized homopolymeric acrylamide are obtained by allowing asuitable amount of formamide to remain in the film, e. g., from 1 to 2%to or or more by weight of the fihn.

If water-resistant films are desired, they can be obtained by immersingthe film (before or after removal of all or part of the formamide) in anaqueous solution of formaldehyde to form the N-methylol derivative ofthe polyacrylamide, followed by heating at l20l50 C. to obtain awater-insoluble, cross-linked material.

Example 2 One (1) gram of a dry, ground copolymer of about acrylamideand 10% acrylic acid is added to ml. of formamide. The resulting mixtureis heated to C. for 30 minutes, yielding a swollen acrylamideacrylicacid copolymer. When the swollen mass is allowed to remain in the excessformamide for one week at room temperature (2 30C.), a clear homogeneoussolution is obtained.

Example 3 Same as in Example 2 with the exception that there is employeda dry, finely divided copolymer of about 75% acrylamide and 25% of (a)vinyl acetate, or (b) methyl acrylate, or (c) styrene, or (d)methacrylonitrile, or (e) methacrylamide. Similar results are obtained.

Example 4 Same as in Example 4 with the exception that there is used 100ml. of a 50/50, by volume, mixture of formamide and ethylene glycol.Similar results are obtained.

Example 6 Same as in Example 4 with the exception that there is used 100ml. of approximately a 50/50 mixture, by volume, of formamide and urea.Similar results are obtained.

Example 7 Same as in Example 4 with the exception that there is used 100ml. of approximately a 50/50 mixture, by volume, of glacial acetic acidand urea. Similar results are obtained.

Example 8 Ninety-nine (99) parts of crystalline urea is heated on a hotplate above 132 C. while the urea melts. To the molten urea is added 1part of the same finely divided homopolymeric acrylamide employed inExample 1. Upon stirring, a clear solution of polyacrylamide dissolvedin the urea is obtained.

(iii

' of combined acrylamide.

Example 9 Same as in Example 8 with the exception that the copolymers ofExample 3 are individually employed instead of the homopolymericacrylamide of Example 8. Similar results are obtained.

Example 10 A mixture of homopolymeric acrylamide and formamide isprepared as in Example 1. When this mixture is heated at 120 C. for 30minutes, partial solution of the polymer in the formamide results.Complete solution of the polymer in the formamide occurs after furtherheating at this same temperature.

It will be understood, of course, by those skilled in th art that ourinvention is not limited to the specific ingredients and method ofeffecting solution of the polymer or copolymer of acrylamide that aregiven by way of illustration in the foregoing examples. Thus, instead ofthe specific comonomers employed in Examples 2, 3, and 9 in formingcopolymers with acrylamide, we may use any other cornonomer which iscopolymerizable With acrylamide in the proportions hereinbefore setforth, that is, in proportions such that the finished copolymer containsin the molecules thereof at least 75% by weight Numerous examples ofsuch comonomers were given previously in the specification.

The advantages of the present invention will be immediately apparent tothose skilled in the art from the foregoing description. The inventionbroadens the field of utility of polyacrylamide, since it providessolvents and plasticizers therefor, other than water, and thus makes theresulting compositions suitable in applications for which aqueoussolutions of polyacrylamide would be entirely unsuited. As is wellknown, aqueous solutions of polyacrylamide are polar and have a highdielectric constant; consequently such solutions are entirely unsuitablefor many applications.

As a result of the present invention all of the inherent advantages of anon-aqueous solvent or swelling agent can be utilized in working withpolyacrylamide (homopolymeric acrylamide) and with copolymers ofacrylamide containing at least about 75 of acrylamide combined in thepolymer molecule. For instance, the invention provides compositionswhich can be extruded or otherwise shaped to form useful articles ofmanufacture. The compositions of the present invention are also usefulin warp-sizing and other textile-treating applications, as well as inadhesive compositions, ceramic binders, nitrocellulose lacquers, ascomponents of rubberbased glues, in furniture glues which are capable ofwithstanding freeze-thaw cycles, in making chemical analyses of polymersand copolymers of acrylamide where it is desired to make the analysis ina non-aqueous solvent for the acrylamide polymerization product, and

, for various other purposes, many examples of which have been givennereinbefore.

We claim:

1. A composition of matter comprising (1) a polymer of acrylamidecontaining in the polymer molecules an average of at least 75 by weightof combined acrylamide and (2) at least one amide selected from theclass consisting of urea and formamide, said urea being in molten statewhen it is used alone with the said polymer of acrylamide.

2. A composition as in claim 1 wherein the polymer acrylamide ishomopolymeric acrylamide.

3. A composition as in claim 1 wherein the polymer of acrylamide is acopolymer containing, combined in the molecules thereof, an average ofat least 75% by weight of acrylamide and an average of up to 25% byweight of a different compound containing a CHz=C grouping.

4. A composition as in claim 1 wherein the polymer of acrylamide of (l)constitutes at least 1% by weight of the composition.

5. A composition of matter comprising (1) a polymer of acrylamidecontaining in the polymer molecules an average of at least 75% by weightof combined acrylamide and (2) molten urea.

6. A composition of matter comprising (1) a polymer of acrylamidecontaining in the polymer molecules an average of at least 75 by weightof combined acrylamide and (2) formamide. I

7. A composition of matter comprising (1) a polymer of acrylamidecontaining in the polymer molecules an average of at least 75 by weightof combined acrylamide and (2) molten urea, the polymerization productof (l) constituting from about 5% to about 30%, by weight, of the totalamount of (1) and (2).

V 8. A composition of ,matter comprising (1) a polymer of acrylamidecontaining in the polymer molecules an average of at least 75 by weightof combined acrylamide and (2) formamide, the polymerization product of(1) constituting from about 5% to about 30%, by weight, of the totalamount of (1) and (2).

9. A plasticized composition comprising a polymer of acrylamidecontaining in the polymer molecules an average of at least 75 by weightof combined acrylamide, said polymerization product being plasticizedwith a plasticizing amount not substantially exceeding 40% by weight ofthe composition of a plasticizer comprising at least one amide selectedfrom the class consisting of urea and formamide, said ureabeing inmolten state when it is used alone with the said polymer of acrylamide,

10. A composition comprising a plasticized polymer of acrylamidecontaining in the polymer molecules an average of at least 75 by weightof combined acrylamide, said polymerization product being plasticizedwith from about 1% to about 35% by weight of the whole of molten urea. gp

11. A composition comprising a plasticized polymer of acrylamidecontaining in the polymer molecules an average of at least 75 by weightof combined acrylamide,

said polymerization product being plasticized with from about 1% toabout 35% by weight of the whole. of formamide.

References Cited in the file of this patent UNITED STATES PATENTS2,620,324 Coover Dec. 2, 1952

1. A COMPOSITION OF MATTER COMPRISING (1) A POLYMER OF ACRYLAMIDECONTAINING IN THE POLYMER MOLECULES AN AVERAGE OF AT LEAST 75% BY WEIGHTOF COMBINED ACRYLAMIDE AND (2) AT LEAST ONE AMIDE SELECTED FROM THECLASS CONSISTING OF UREA AND FORMAMIDE, SAID UREA BEING IN MOLTEN STATEWHEN IT IS USED ALONE WITH THE SAID POLYMER OF ACRYLAMIDE.